/*

* Copyright (c) 2008 Nokia Corporation and/or its subsidiary(-ies).

* All rights reserved.

* This component and the accompanying materials are made available

* under the terms of "Eclipse Public License v1.0"

* which accompanies this distribution, and is available

* at the URL "http://www.eclipse.org/legal/epl-v10.html".

*

* Initial Contributors:

* Nokia Corporation - initial contribution.

*

* Contributors:

*

* Description:

*

*/

package com.nokia.mj.impl.utils;

public class Base64

{

    private final static byte[] ENCODE_ALPHABET =

    {

        (byte)'A', (byte)'B', (byte)'C', (byte)'D', (byte)'E', (byte)'F', (byte)'G',

        (byte)'H', (byte)'I', (byte)'J', (byte)'K', (byte)'L', (byte)'M', (byte)'N',

        (byte)'O', (byte)'P', (byte)'Q', (byte)'R', (byte)'S', (byte)'T', (byte)'U',

        (byte)'V', (byte)'W', (byte)'X', (byte)'Y', (byte)'Z',

        (byte)'a', (byte)'b', (byte)'c', (byte)'d', (byte)'e', (byte)'f', (byte)'g',

        (byte)'h', (byte)'i', (byte)'j', (byte)'k', (byte)'l', (byte)'m', (byte)'n',

        (byte)'o', (byte)'p', (byte)'q', (byte)'r', (byte)'s', (byte)'t', (byte)'u',

        (byte)'v', (byte)'w', (byte)'x', (byte)'y', (byte)'z',

        (byte)'0', (byte)'1', (byte)'2', (byte)'3', (byte)'4', (byte)'5',

        (byte)'6', (byte)'7', (byte)'8', (byte)'9', (byte)'+', (byte)'/'

    };

    private final static byte[] DECODE_ALPHABET =

    {

        -9,-9,-9,-9,-9,-9,-9,-9,-9,                 // Decimal  0 -  8

        -5,-5,                                      // Whitespace: Tab and Linefeed

        -9,-9,                                      // Decimal 11 - 12

        -5,                                         // Whitespace: Carriage Return

        -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,     // Decimal 14 - 26

        -9,-9,-9,-9,-9,                             // Decimal 27 - 31

        -5,                                         // Whitespace: Space

        -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,              // Decimal 33 - 42

        62,                                         // Plus sign at decimal 43

        -9,-9,-9,                                   // Decimal 44 - 46

        63,                                         // Slash at decimal 47

        52,53,54,55,56,57,58,59,60,61,              // Numbers zero through nine

        -9,-9,-9,                                   // Decimal 58 - 60

        -1,                                         // Equals sign at decimal 61

        -9,-9,-9,                                      // Decimal 62 - 64

        0,1,2,3,4,5,6,7,8,9,10,11,12,13,            // Letters 'A' through 'N'

        14,15,16,17,18,19,20,21,22,23,24,25,        // Letters 'O' through 'Z'

        -9,-9,-9,-9,-9,-9,                          // Decimal 91 - 96

        26,27,28,29,30,31,32,33,34,35,36,37,38,     // Letters 'a' through 'm'

        39,40,41,42,43,44,45,46,47,48,49,50,51,     // Letters 'n' through 'z'

        -9,-9,-9,-9                                 // Decimal 123 - 126

    };

    private final static byte WHITE_SPACE_ENC = -5;

    private final static byte EQUALS_SIGN_ENC = -1;

    private final static byte EQUALS_SIGN = (byte)'=';

    public static byte[] decode(String s)

    {

        if (s == null)

        {

            return null;

        }

        byte[] source = s.getBytes();

        int    len34   = source.length * 3 / 4;

        byte[] outBuff = new byte[ len34 ];

        int    outBuffPosn = 0;

        byte[] b4        = new byte[4];

        int    b4Posn    = 0;

        int    i         = 0;

        byte   sbiCrop   = 0;

        byte   sbiDecode = 0;

        for (i = 0; i < source.length; i++)

        {

            sbiCrop = (byte)(source[i] & 0x7f);

            sbiDecode = DECODE_ALPHABET[ sbiCrop ];

            if (sbiDecode >= WHITE_SPACE_ENC)

            {

                if (sbiDecode >= EQUALS_SIGN_ENC)

                {

                    b4[ b4Posn++ ] = sbiCrop;

                    if (b4Posn > 3)

                    {

                        outBuffPosn += decode4to3(b4, 0, outBuff, outBuffPosn);

                        b4Posn = 0;

                        if (sbiCrop == EQUALS_SIGN)

                            break;

                    }

                }

            }

            else

            {

                return null;

            }

        }

        if (outBuffPosn == 0)

        {

            return null;

        }

        byte[] out = new byte[ outBuffPosn ];

        System.arraycopy(outBuff, 0, out, 0, outBuffPosn);

        return out;

    }

    public static String encode(byte[] source)

    {

        if (source == null)

        {

            return null;

        }

        int len = source.length;

        int    len43   = len * 4 / 3;

        byte[] outBuff = new byte[(len43) + ((len % 3) > 0 ? 4 : 0)];

        int d = 0;

        int e = 0;

        int len2 = len - 2;

        int lineLength = 0;

        for (; d < len2; d+=3, e+=4)

        {

            encode3to4(source, d, 3, outBuff, e);

            lineLength += 4;

        }

        if (d < len)

        {

            encode3to4(source, d, len - d, outBuff, e);

            e += 4;

        }

        if (outBuff.length == 0)

        {

            return null;

        }

        return new String(outBuff, 0, e);

    }

    private static int decode4to3(byte[] source, int srcOffset, byte[] destination, int destOffset)

    {

        if (source[ srcOffset + 2] == EQUALS_SIGN)

        {

            int outBuff = ((DECODE_ALPHABET[ source[ srcOffset    ] ] & 0xFF) << 18)

                          | ((DECODE_ALPHABET[ source[ srcOffset + 1] ] & 0xFF) << 12);

            destination[ destOffset ] = (byte)(outBuff >>> 16);

            return 1;

        }

        else if (source[ srcOffset + 3 ] == EQUALS_SIGN)

        {

            int outBuff = ((DECODE_ALPHABET[ source[ srcOffset     ] ] & 0xFF) << 18)

                          | ((DECODE_ALPHABET[ source[ srcOffset + 1 ] ] & 0xFF) << 12)

                          | ((DECODE_ALPHABET[ source[ srcOffset + 2 ] ] & 0xFF) <<  6);

            destination[ destOffset     ] = (byte)(outBuff >>> 16);

            destination[ destOffset + 1 ] = (byte)(outBuff >>>  8);

            return 2;

        }

        else

        {

            try

            {

                int outBuff = ((DECODE_ALPHABET[ source[ srcOffset     ] ] & 0xFF) << 18)

                              | ((DECODE_ALPHABET[ source[ srcOffset + 1 ] ] & 0xFF) << 12)

                              | ((DECODE_ALPHABET[ source[ srcOffset + 2 ] ] & 0xFF) <<  6)

                              | ((DECODE_ALPHABET[ source[ srcOffset + 3 ] ] & 0xFF));

                destination[ destOffset     ] = (byte)(outBuff >> 16);

                destination[ destOffset + 1 ] = (byte)(outBuff >>  8);

                destination[ destOffset + 2 ] = (byte)(outBuff);

                return 3;

            }

            catch (Exception e)

            {

                return -1;

            }

        }

    }

    private static byte[] encode3to4(byte[] source, int srcOffset, int numSigBytes, byte[] destination, int destOffset)

    {

        int inBuff = (numSigBytes > 0 ? ((source[ srcOffset ] << 24) >>>  8) : 0)

                     | (numSigBytes > 1 ? ((source[ srcOffset + 1 ] << 24) >>> 16) : 0)

                     | (numSigBytes > 2 ? ((source[ srcOffset + 2 ] << 24) >>> 24) : 0);

        switch (numSigBytes)

        {

        case 3:

            destination[ destOffset     ] = ENCODE_ALPHABET[(inBuff >>> 18)];

            destination[ destOffset + 1 ] = ENCODE_ALPHABET[(inBuff >>> 12) & 0x3f ];

            destination[ destOffset + 2 ] = ENCODE_ALPHABET[(inBuff >>>  6) & 0x3f ];

            destination[ destOffset + 3 ] = ENCODE_ALPHABET[(inBuff) & 0x3f ];

            return destination;

        case 2:

            destination[ destOffset     ] = ENCODE_ALPHABET[(inBuff >>> 18)];

            destination[ destOffset + 1 ] = ENCODE_ALPHABET[(inBuff >>> 12) & 0x3f ];

            destination[ destOffset + 2 ] = ENCODE_ALPHABET[(inBuff >>>  6) & 0x3f ];

            destination[ destOffset + 3 ] = EQUALS_SIGN;

            return destination;

        case 1:

            destination[ destOffset     ] = ENCODE_ALPHABET[(inBuff >>> 18)];

            destination[ destOffset + 1 ] = ENCODE_ALPHABET[(inBuff >>> 12) & 0x3f ];

            destination[ destOffset + 2 ] = EQUALS_SIGN;

            destination[ destOffset + 3 ] = EQUALS_SIGN;

            return destination;

        default:

            return destination;

        }

    }

}